Really Mr Red Shoe. Do you understand that was all a joke? Not understanding humor is one of the first signs of a serious mental health issue. I do not say this as an insult - my wife does this stuff for a living.

Companies that have been in business for a long time rarely propose bogus solutions to the use of their products, especially one that has been in use for decades...lots of successful outcomes when there is a reasonably workman like install. That a product can fail if it is not used properly should be a given. To point out or express that it is certain to fail without any substantiation is wrong. All the examples of drywall failing when not used according to an accepted, tested procedure with thousands of successful results and independent test results showing it working is just wrong. There is more than one way that has been tested and approved to use Kerdi to make a shower, but it is up to the installer to decide what he is comfortable to use, but any of those materials will work. If you don't trust your plumbing skills, a cbu backer may not prevent eventual failure, as a slow leak could easily end up with the floor and studwalls rotting out before you noticed. Not counting that wet wood is a magnet to carpenter ants and termites which bring their own problems.

Letting that advice stand where the fellow has slope issues with the Kerdi pan. Both you and Jim make me sick.

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The suggested answer, should you choose to check verses bashing everyone for no cause, is to tear the foam pan out and start over. As opposed to here, where John Whipple thinks he is the only one that should give advice, there are LOTS of people, well qualified, that can and do offer advice on www.johnbridge.com. And, when they give that advice, they don't do it in insulting and promoting themselves as superior and the only one that knows anything.

Two days after this advice was not given. After I emailed you. After I email Dana.

You make me sick.

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I do not read every message on every board. I also do not read messages from you - why would I, the most I get from you is insults.

In the situation above, the OP failed to follow the instructions when installing a foam tray - he tried to install it over a non-level subfloor. The instructions clearly say to ensure the floor is level before installing it. He tried to do it with thinset, then stood on the thing to embed it and do other work...well, what you'd expect happened...it sunk, negating the effort to do it his way, rather than the way the instructions said. Sort of like John Whipple not following Schluter's NA instructions. I wonder if he ever thought about the fact that thinsets in the USA meet one spec, and those sold in Europe meet a different one. The manufacturer's instructions differ because the materials differ...but, to extrapolate that to infer that the NA instructions are inadequate, is not a valid, logical result. What is logical is that the manufacturer tells people how to install their products with the materials available such that the end result is reliable. Creating fear and uncertainty is one way to make yourself look superior, when in fact, it has no substantiation. I've been trying to get a copy of the European thinset specification, but I'm not willing to pay over $100 for it...I'm still looking. What I expect is that the filler size (sand, etc.) and minimum cement volume in the thinsets sold between the NA and European markets differ, and that given the specs, thinset alone cannot make a fully reliable, waterproof seam in Kerdi with the European spec thinset like it can in the USA, and in order to ensure it is waterproof, they call for seaming it different.

But, John takes the difference to infer and promote question that one is superior to the other.

If I do get a copy of both specs, I'll try to summarize the differences in a separate thread. But, in the meantime, I believe the manufacturer knows his product and what it takes to make it work...John doesn't. Thinsets in the USA are rated according to A118.x and in Europe according to BS EN 12004.

Since no one around here has ever seen or heard of a Kerdi Shower failure, a thread was started over at John Bridges site. All this talk of drywall failure as an academic exercise is all well and good, of course, but unless there are actual failures it's a solution lookin for a problem [that simply doesn't exist].

For those that aren't keeping up, the Kerdiboard failure was in a steam shower, likely where a steam line was too close to the board. The manual calls for a max temp around Kerdiboard of about 170-degrees (I'd have to look up the exact number, but that's close). Steam, boiling water, happens at 212-degrees at sea level. And, steam could be hotter than that once it is a gas, there's no practical limit on the temp it can raise. As far as I know, no final outcome on that situation.

There's no evidence of an actual failure in the stone like shower shown, either. If that area is where the spray hits the wall, a natural stone can become saturated. There's no evidence that there is any leaks to the outside or structural failure.

A foam Kerdi shower pan, if you read the instructions, says prior to installation, the floor must be level. Because you stand on the thing to embed it into the thinset, it is essentially impossible to try to level it with thinset and get a good bond to the substrate. Trying to level the pan afterwards is a very difficult thing to do, and the time involved and the reliability of the fix afterwards is beyond the scope of most DIY'ers, thus the recommendation to tear it out and start over.

With the unprotected drywall, no question, that's just dumb. The difference is day and night. Done right, a Kerdi shower doesn't leak. Mold takes three things, eliminate any one, and it does not occur: moisture, food, mold spores. Kerdi, done right, eliminates moisture from anything behind it, and since it isn't food, nor is mortar or tile, mold will only happen if things aren't kept clean, and then on the surface...that can happen on ANY shower, regardless of how it is built.

More pictures of tile directly on drywall...anyone that knows anything expects them to do nasty things if moisture is involved, but again, once covered with Kerdi, a waterproof material, it's no different than the drywall on your ceiling under your roof, or that on your walls next to the windows or doors. When installed properly as a system, the drywall never gets wet. http://www.schluter.com/media/shower-handbook.pdf?v=201401311539 I didn't make the recommendation up...Schluter did, and feels strongly enough about it to have had it tested and certified as waterproof by a well-respected testing agency, and backs it up with a decent warranty AND HAS BEEN DOING IT THIS WAY IN THE USA FOR DECADES. In the process, they also built waterproof showers with cbu and a few other materials, all called out in the referenced link, should you not trust yourself. But, if you didn't trust yourself to do it right, or don't want to read and understand their instructions, you may want to use a different material. A conventionally built shower can perform well, but loses the advantage of limiting any moisture to right under the tile like in a Kerdi shower. Lots more conventional showers can be found that have leaked if you look around than Kerdi ones, simply because it is not all that hard to build one that does not leak.

Schluter is the only company with the long track record of successful showers done per their instructions (over 20-years), and believes enough in their product to safely make use of the less expensive, more easily installed material. The do not tell you you MUST use drywall, but that you can, and have a successful installation. Why spend money on extras when the success rate is identical, it goes up faster, and the end result comes out the same...a waterproof shower. I've said more than once, you do not have to use drywall in your shower when using Kerdi, but that you safely can if you are anywhere near a bit handy and can read and understand the pretty simple instructions and general guidelines on its use.